Mantis#2566. Thank you kindly, Diva for a patch that:

This patch introduces a couple of read-only properties, 
so that I can grab the asset server plugin from a region 
module. This is needed to set up an http service for 
accessing standalone assets remotely.

OpenSim/Framework/Communications/Cache/AssetCache.cs

@@ -85,6 +85,11 @@ namespace OpenSim.Framework.Communications.Cache
         /// </summary>
         private readonly IAssetServer m_assetServer;
 
+        public IAssetServer AssetServer
+        {
+            get { return m_assetServer; }
+        }
+
         /// <summary>
         /// Report statistical data.
         /// </summary>

OpenSim/Framework/Communications/Cache/AssetServerBase.cs

@@ -45,6 +45,11 @@ namespace OpenSim.Framework.Communications.Cache
         protected Thread m_localAssetServerThread;
         protected IAssetProviderPlugin m_assetProvider;
 
+        public IAssetProviderPlugin AssetProviderPlugin
+        {
+            get { return m_assetProvider; }
+        }
+
         // Temporarily hardcoded - should be a plugin
         protected IAssetLoader assetLoader = new AssetLoaderFileSystem();